Can bootstrap also be used for web design (as an alternative to photoshop) or is it just all about development?

Answer 1

Bootstrap isn't an alertnative to photoshop ^^
Both can be used for web designing, but for differents purposes: Bootstrap style your page elements through css framework, while Photoshop make visual elements for styling page elements through css ( framework or not )...
Bootstrap handle css, Photoshop handle bitmaps: they are totally different :P

Answer 2

Yes Bootstrap Can be Used, i recommend you to use Bootstrap.